1. Field of the Invention
The present invention relates to a cuvette used for spectrophotometrical analyses, in which electromagnetic energy is passed through a liquid sample contained therein, such as a pure liquid, a solution, a dispersion, a colloidal solution or the like.
2. Description of the Prior Art
In such a cuvette the radiation beam generally enters the cuvette through one transparent end of the cuvette and exits the cuvette at the opposite end thereof, which end normally is an open end in direct contact with the surrounding environment. The characteristics of the beam emerging from the cuvette are then analysed to determine the composition of the fluid through which the radiation beam has passed and which is contained in the cuvette. Since the radiation beam has to pass through the cuvette, the transparent material thereof may cause artefacts such as scattering of the radiation beam, i.e. the determination of the composition of the fluid is dependable on the material of the cuvette.
EP 0 732 578 discloses a sample holder used for spectroscopy and is provided with a net, on which a sample liquid is applied. The fluid is applied in such a way that the liquid is spread over the mesh of the net. A radiation beam is passed through the liquid perpendicular thereto and the transmitted radiation is detected. The object of this disclosed sample holder is to properly dose the liquid to be radiated. This is done by securing that always the same amount of liquid will be absorbed in each mesh. The amount liquid present in the mesh of the net is then derived from a net constant. Even if the detected radiation through the liquid is independent of the material of the holder, the mesh can only hold a very small amount of liquid, i.e. only a film of liquid, and has not the capability to hold any larger quantities of liquid. JP-62-229046 discloses a particle detector comprising a fluid container provided with a porous film at the bottom end thereof. The porous film is designed to permit air/gas to pass there through, but prevent the fluid contained in the container to pass there through. It is the surface tension of the liquid that allows it to be kept in the container. The fluid container in this JP patent is presumably designed to be able to press gas through the bottom of the container without any leaking of fluid from the container.
U.S. Pat. No. 3,936,196 discloses a fluid chamber having manipulatable window elements. The chamber is provided with two transparent plates in order to permit light to enter and leave the chamber. This application recognises the problem that the material that the light has to pass on its way in and out of the chamber may impair the results obtained, when analysing the radiation passed through the chamber. This is especially true when the chambers contain gaseous materials, in which case a clouding or fogging of the transparent plate occurs. The fogged plate has then to be removed and cleaned before a new analyse can be performed. The fluid chamber according to the invention in this U.S. patent solves this problem by improving the structure of the transparent plate and thereby reduce the required frequency of cleaning or replacement of the plate to maintain a light transmittive area free of fogging.
Even if there have been made some attempts in prior art to increase the accuracy of spectrophotometrical analyses done on liquids, such as pure liquids, solutions, dispersions, colloidal solutions or the like, contained in a cuvette, there still is a need to make the spectrophotometrical analyses truly independent of the cuvette material.